Assembly of a Blade and a Composite Carrier, Obtained by Sealing

ABSTRACT

The invention relates to a mechanical assembly ( 1 ) for the field of aeronautics, including: a part ( 3 ) comprising an attachable end; a recess for receiving the part ( 3 ), said recess having a wall ( 2 ) comprising an organic matrix composite or OMC; and a sealing composite ( 4 ) including a thermoplastic or heat-curable material including 0 to 70 wt % of a filler and forming a mechanical and/or physicochemical link between the part ( 3 ) and the recess having the OMC wall ( 2 ).

FIELD OF THE INVENTION

The present invention relates to the technical field of assemblies in the aeronautics sector, especially in turbomachine compressor rectifiers. In particular, the invention relates to a (stage of a) turbomachine compressor rectifier made up of parts of an organic matrix composite and made up of at least one blading subassembly incorporating a mechanical assembly achieved by sealing.

In the context of the present invention, “sealing” refers to the operation of fastening a part in a carrier by means of a polymer element, which may include filler or not, by mechanical locking and/or physicochemical interaction with the carrier and/or the part to be attached.

TECHNOLOGICAL BACKGROUND AND STATE OF THE ART

In the current art, there are no turbomachine compressor rectifiers made of composite material, but rather only made of a metal material, for example titanium (TA6V), steel or aluminum.

Furthermore, the blades generally have a single material and profile on a same stage, possibly with small variation in the calibration angle for aerodynamic reasons on the last stage.

Lastly, the current systems rest on an outer shroud, serving as a casing that performs most of the mechanical functions, on blades attached to a first end on those outer shrouds by various assembly technologies (welding, riveting, bolting), and on relatively flexible inner shrouds attached to the blades at a second end but that do not perform any structural function.

Today, one of the major problems of the use of composite parts lies in their interface with the outside. The invention proposes a solution for assembling parts of various natures: either “metal/composite” or even “composite/composite” hybrids, while using the smallest possible quantity of metal attachment means, the latter creating many issues (mass, differential expansion, etc.).

Document EP 1 493 901 discloses an assembly between blades and the inner shroud of a compressor rectifier of an aeronautic engine. Each blade passes through an opening formed in the inner shroud and is attached thereto using sealing cement containing an organic polymer adhesive.

Document EP 1 081 335 discloses a stator assembly for a rotary machine and, more specifically, the assembly of stator blades to inner shroud abradables. The stator assembly comprises a thermoplastic shoulder provided with an opening designed to receive the foot of the stator blade, and the elastomer abradable connected to the shoulder using adhesives.

Document DE 10 2009 010 613 discloses a method for producing a closed strip around the blades of a turbine. A strip of fibrous material is inserted into a housing arranged at the free end of the blades, and a matrix is infiltrated in the fibrous material of the strip and polymerized to form a composite.

Document FR 1 431 558 discloses a blade structure comprising a case and two concentric enclosures, an outer enclosure and an inner closure, the latter being offset from the outer enclosure by separating means. The blades are mounted gripped in holes formed facing each other in both enclosures. The blades may be welded, glued or fastened on the outer enclosure, which is mounted gripped in an outer case. In particular, all these parts of the blade structure may be made of synthetic resin and glued to one another. The blades may also be made of metal and welded on the outer case.

AIMS OF THE INVENTION

The present invention aims to overcome the drawbacks of the state of the art.

In particular, the invention aims to allow the production of bladed rectifiers with a light weight and at a low cost for all compressors whose rotor is made up of discs, of a drum, or of other elements.

The invention also aims to allow the easy assembly of rectifier blades with varied properties, so as to best optimize the mechanical strength as well as the costs.

The invention also aims to allow the rectifier to be easily assembled and disassembled, thereby favoring the in-use maintenance aspects while limiting the number of metal fastening elements.

The invention also aims to save time during the assembly of the compressor.

The invention lastly aims to allow permanent and non-deformable connection of the metal or OMC (organic matrix composite) composite parts to parts made of OMC composite.

MAIN CHARACTERISTIC ELEMENTS OF THE INVENTION

A first object of the present invention most generally relates to a mechanical assembly in the aeronautics field comprising:

-   a part comprising an attachable end; -   a recess with a wall of an organic matrix composite or OMC for     receiving the part; -   a sealing composite comprising a thermoplastic or heat-sealable     material with between 0 and 70 wt % of a filler, preferably with     short fibers, forming a mechanical and/or physicochemical connection     between said part and the recess with the OMC wall.

According to specific embodiments of the invention, the mechanical assembly comprises at least one or a suitable combination of the following features:

-   said part is a blade; -   said part comprises one end (or foot) whose geometry allows to     optimize the mechanical connection; -   said part comprises a foot geometry; -   the recess with the OMC wall is a profiled carrier, preferably in     the shape of a “U”; -   the organic matrix of the recess is made of a thermoplastic or     heat-sealable material; -   the material of the recess with the OMC wall and that of the sealing     composite are identical or chemically compatible, so as to produce a     chemical or physicochemical attachment between them; -   the recess with the heat-sealable or thermoplastic OMC wall is     produced by a method selected from the group consisting of     compression molding, injection of thermoplastic or heat-sealable     matrix, heat sealing and co-consolidation; -   the sealing composite to be injected is produced by a method     selected from the group consisting of injection of thermoplastic or     heat-sealable matrix with or without filler and of compression     molding.

A second object of the present invention relates to a rectifier stage for a turbomachine compressor comprising a mechanical assembly of a plurality of blades to a housing with an OMC wall imparting structural rigidity to the assembly, according to the above principle, the blades each comprising a foot, said recess with an OMC wall and said sealing composite cooperating to seal the feet of the blades in the recess.

According to specific embodiments of the invention, the rectifier stage comprises at least one or a suitable combination of the following features:

-   the mechanical assembly is in the form of a ring or of a sector     attached to an outer shroud of the rectifier stage by means of     mechanical fasteners; -   the mechanical fasteners are lock bolts; -   the blades are made of metal or composite material; -   the blades are made of titanium or aluminum.

A third object of the invention relates to a turbomachine compressor comprising one or more rectifier stages as described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective view of an assembly as in the invention and the related parts.

FIG. 2 diagrammatically shows the composite assembly of the invention, by thermoforming followed by overinjection, in a side view and a front view, respectively.

Key

-   1. Basic structural pattern -   2. U-shaped profile -   3. Blade -   3A. Blade foot -   4. Sealing material

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

The assembly as in a preferred embodiment of the present invention, whose principle and parts are shown in a perspective view in FIG. 1, is essentially made up of a subassembly 1 obtained by the sealing of a mechanical type between:

-   a part 2, which is preferably profiled, still more preferably in the     shape of a “U,” with a base of an organic matrix composite (OMC)     material that is heat-sealable or thermoplastic, imparting     structural rigidity to the assembly, and -   a blade 3 made of an a priori non-specific material (metal or     composite) and comprising a foot whose geometry may vary or be     adapted as needed. -   Other diagrammatic views of this assembly are shown in FIG. 2.

According to the present invention, the composite carrier with heat-sealable or thermoplastic matrix 2 may be manufactured by any type of method allowing to obtain sufficient mechanical properties, such as for example: compression molding, injection of a thermoplastic or heat-sealable matrix, for example RTM (resin transfer molding), thermoforming or co-consolidation, etc. However, the invention is not limited to the use of a profiled part 2, for example in the shape of a “U”. Thus, a planar carrier may also be considered.

The sealing fastening composite or sealing composite or sealing material 4 has a base of a heat-sealable or thermoplastic matrix with between 0 and 70% of fibers, for example or preferably short fibers, and may be implemented by a method for injecting a thermoplastic or heat-sealable matrix or by compression molding. More generally, the filler may be any suitable mineral or organic filler. Thus, the matrix may nevertheless have a filler (with fibers) or not have a filler (pure matrix, 0% fibers).

Still according to the invention, the particular geometry of the foot of the blade 3A ensures that it is positioned and maintained in the structure (FIG. 2). The blades 3 being sealed, the blade foot 3A is then embedded by the fastening composite 4 mentioned above, which for example fills the profiled part 2 and thereby ensures that the blade 3 is maintained.

The sealing or assembly technique used as in a preferred embodiment of the invention for metal blades 3 is illustrated more particularly and very diagrammatically in FIG. 2. The structural part or carrier structure 2 is provided by a U-shaped profile part 2 made of a thermoplastic composite with long fibers obtained by thermoforming (the opening of the “U” is oriented toward the outside relative to the blade).

Thermoplastic resin with a short fiber filler 4 is injected to fill the hollow volume that remains once the foot of the blade 3A is positioned in the carrier structure 2.

Furthermore, in order to best satisfy the aerodynamic constraints, material is over-injected at the level of the areas that do not allow to obtain the geometry by thermoforming (not shown). Filling with the sealing material to produce the mechanical and/or physicochemical connection is for example achieved in a second step or, if possible, at the same time as the composite structural part is produced.

According to the present invention, the material of the U-shaped composite carrier 2 and the sealing material 4 are identical or chemically compatible (for example, thermoplastic materials of the same nature), so as to produce chemical attachment between them. The resulting “material” connection ultimately amounts in only producing a single homogenous part, which is an additional advantage in terms of mechanical strength of the assembly.

According to still another preferred embodiment of the invention, the subassembly 1 belonging to the rectifier stage is in the shape of a ring or of a sector fastened to an outer shroud or to a case by means of mechanical fasteners, such as lock bolts (not shown).

If differential expansion problems appear, for example between bladed sectors, intermediate parts, that may be deformable or not, may be inserted radially or circumferentially into the assembly.

The advantages of the concept as in the invention for producing turbomachine rectifiers are the following:

-   reduced mass relative to the prior art, thanks to the use of     composites for the cases and possibly for the bladings; -   limited production cost, thanks to a smaller number of parts and     easy assembly; -   the static part of the booster (compressor) is more simply and more     cost-effectively repaired, the simple replacement of a blade sector     being much easier than in the case of the most common current     architectures (for example, welded titanium assembly); and -   the production of finished parts without reworking after leaving the     mold. 

1. A mechanical assembly (1) in the aeronautics field comprising: a part (3) comprising an attachable end; a recess with a wall comprising an organic matrix composite or OMC (2) for receiving the part (3); a sealing composite (4) comprising a thermoplastic or heat-sealable material with between 0 and 70 wt % of a filler, forming a mechanical and/or physicochemical connection between said part (3) and the recess with the OMC wall (2).
 2. The assembly as in claim 1, wherein said part (3) is a blade.
 3. The assembly as in claim 1, wherein said part (3) comprises one end whose geometry allows to optimize the mechanical and/or physicochemical connection.
 4. The assembly as in claim 3, wherein said part (3) comprises a foot geometry.
 5. The assembly as in claim 1, wherein the recess with the OMC wall (2) is a profiled carrier, preferably in the shape of a “U”.
 6. The assembly as in claim 1, wherein the organic matrix of the recess (2) is made of a thermoplastic or heat-sealable material.
 7. The assembly as in claim 1, wherein the material of the recess with the OMC wall (2) and that of the sealing composite (4) are identical or chemically compatible, so as to produce a chemical or physicochemical attachment between them.
 8. The assembly as in claim 6, wherein the recess with the heat-sealable or thermoplastic OMC wall (2) is produced by a method selected from the group consisting of compression molding, injection of thermoplastic or heat-sealable matrix, heat sealing and co-consolidation.
 9. The assembly as in claim 1, wherein the sealing composite (4) to be injected is produced by a method selected from the group consisting of injection of a thermoplastic or heat-sealable matrix with or without filler, and of compression molding.
 10. A rectifier stage for a turbomachine compressor comprising a mechanical assembly (1) of a plurality of blades (3) with a housing having an OMC wall (2) imparting structural rigidity to the assembly, as in any one of the preceding claims, the blades (3) each comprising a foot (3A), said recess with an OMC wall (2) and said sealing composite (4) cooperating in order to seal the feet (3A) of the blades (3) in the recess (2).
 11. The rectifier stage as in claim 10, wherein the mechanical assembly (1) has the form of a ring or of a sector attached to an outer shroud of the rectifier stage by means of mechanical fasteners.
 12. The rectifier stage as in claim 11, wherein the mechanical fasteners are lock bolts.
 13. The rectifier stage as in claim 10, wherein the blades (3) are made of metal or composite material.
 14. The rectifier stage as in claim 13, wherein the blades (3) are made of titanium or aluminum.
 15. A turbomachine compressor comprising one or more rectifier stages as in claim
 10. 